Low inertia valve lifter unit and method of making the same



April 12, 1960 G. L. CHRISTENSEN Low INERTIA VALVE LIFTER UNIT AND METHOD OF MAKING THE SAME Filed Dec. 2'7, 1957 2 Sheets-Sheet l I INVENTOR. GEORGE Z C #215 reuse/v April 1960 e. L. CHRISTENSEN 2,932,290

- LOW INERTIA VALVE LIFTER UNIT AND METHOD OF MAKING THE SAME Filed Dec. 27, 1957 2 Sheets-Sheet INVENTOR. GEORGE L Cale/srz-zvssw FIG. 7.

M1 UM AGE/v7 FIG: .57

United States Patent Low INERTIA VALVE LIFTER UNIT AND METHOD on MAKING THE SAME George L. Christensen, Torrance, Calif, assignor to Harvey Machine Co., Inc., Los Angeles, Calif., 21 corporation of California This invention has to do with valve lifters or tappets, and relates particularly to the construction of hydraulic valve lifter units, it being a general object of this in- Vention to provide a light weight unit of the type under consideration and which has low inertial values.

Internal combustion engines involve valve trains for opening and closing ports to the cylinders. The valve per se is usually closed by a spring and is opened by means of a mechanical linkage usually in the form of rods and levers operated by a suitable cam. It is very important that the correct amount of lash be maintained in each valve train and hydraulic valve lifter units are used widely for serving this purpose. In actual practice, the clearances are not only affected by the initial size of the parts involved and by the wearing thereof, but also by the thermal expansion and contraction in the parts and all of the related engine structure. Therefore, the hydraulic lifter units are highly desirable and in addition to the normal function of a cam follower, each hydraulic lifter also serves as an automatic adjuster which maintains zero back-lash in the valve train under all operating conditions. By eliminating all lash in the operating linkage and by also providing a cushion of oil to absorb operating shocks, the lifter promotes quite operation and eliminates the need for periodic manual adjustments to compensate for wear of parts.

Hydraulic valve lifter units have varied widely but have remained generally the same in overall construction and function. Said units have been universally made from iron and steel alloys it being important that the cam follower body he of a material compatible with the material of the cam shaft. Further, it is important that a close fit be maintained between the body and the plunger of the unit, and also between the valve and seat, :all as hereinafter described. Since the atomic weight of -iron and its alloys is relatively high, the common valve lifter is of substantial weight, each unit of conventional automotive size weighing approximately 2457 grains. Due to the weight involved in the valve lifter unit per =se, and in all of the moving parts of the valve train, the speed of the valve action is inherently affected and limited or restricted. .In order to effect maximum speed of operation it is necessary to empoly heavy valve springs, and because of the heavy pressures and weight, the parts themselves must be made stronger in order to compensate therefor. As a result of the materials heretofore employed in the construction of hydraulic lifter units, it is apparent that the entire valve train is of substantial Weight accompanied by the attendant slowness of opera- .tion inherent in the weighty parts that are, or must be employed.

Progress has been made in connection with certain portions of the valve train. "For example, relatively light weight rocker arms have apparently been developed with a high degree of success, although the actual savings in weight have been small. Therefore, the present invention, concerned with the valve lifter, offers avenues of substantial improvement since considerable weight is 2 saved resulting in quickness of operation due to the inherent lightness of the parts that have been provided.

It is on object of this invention to provide a satisfactory and commercially practical hydraulic valve lifter .unit of the type under consideration that is of light weight and which is inherently quick in its operation. With the unit that I provide, approximately one half of the weight is saved over like units heretofore provided, all without sacrificing operational characteristics.

It is another object of this invention to provide a valve lifter construction that lends itself to fabrication from materials of relatively low atomic weight, such as for example, aluminum or magnesium. Aluminum, for instance, is satisfactory for the fabrication involved, but is ordinarily of insufficient strength and insufficient surface hardness. Therefore, I provide a construction and process in connection with the fabrication of valve lifter units whereby said aluminum, or like material, is made of sufiicient strength and surface hardness to be operable and feasible and also commercially practical.

it is still another object of this invention to provide a valve lifter unit wherein the major component parts thereof can be extruded. With the construction and method that I provide, the two major components, the cam follower and the plunger, are extruded of light weight material in a manner to increase the density of said material and to the end that the strength of the material is substantially increased.

Further, it is an object of this invention to provide a valve lifter unit wherein the major component parts thereof can be impact extruded. With the construction and method that i provide, the said major components are formed from solid slugs, or blanks, and the bodies of material forming the components are compressed and forced to flow into the desired shape under pressures which substantially increase the density of the components. Said components of increased density are durable under actual operating conditions and are still light in weight.

An object of this invention is to provide a hydraulic valve lifter unit of the character thus far referred to that is simple to construct, which is commercially practical to manufacture and which is reliable in its operation.

The various objects and features of this invention will be fully understood from the following detailed description of a typical preferred form and application of the invention, throughout which description reference is made to the accompanying drawings in which:

Fig. 1 is a transverse sectional view through a typical internal combustion engine and shows a valve train and the application of a hydraulic valve lifter unit as provided by the present invention. Fig. 2 is a vertical sectional view through the lifter unit and taken as indicated by line 2-2 on Fig. 1. Fig. 3 is a vertical sectional view of the plunger of the structure removed from the unit as shown in Fig. 2. Fig. 4 is a vertical sectional view of a portion of the body of the structure removed from the unit as. shown in Fig. 2. Fig. 5 is an exploded perspective view illustrating the base and slug that are assembled in accordance with the invention in order to form the body of the unit. Fig. 6 is a vertical sectional view of the body of the unit prior to machining thereof. Fig. 7 is an exploded perspective view illustrating the valve seat and slug that are assembled in accordance with the invention in order to form the plunger of the unit. Fig. 8 is a plan view of the valve seat taken generally as indicated by line 8-8 on Fig. 7. Fig. 9 is a vertical sectional ,view of the plunger of the unit prior to machining thereof,

and Fig. 10 is an enlarged fragmentary sectional view showing where the body and plunger are hardened.

The low inertia valve unit and method of making the same that I have provided is particularly useful to the .movement with a minimum of clearance.

is the gear train lightened by the lesser weight of the lifter unit but with this decrease in weight each of the other parts involved can be lightened proportionately as circumstances allow. As a result, the entire valve train is affected and is quicker acting due to the low inertia values of the parts thereof.

The valve lifter Y is housed in a body A which is the cam follower, there being a plunger B operable in the body. The body A and the plunger B are slidably related and ground to very close limits, each plunger B being selectively fitted to each body A to assure free A push rod seat C is free to move with the plunger B in the body A and, as its name implies, it provides a seat to support the lower end of the push rod R.

The plunger B and seat C are pressed toward the upper end of the lifter body A by a coil spring 'which also holds a check ball retainer 11 against the lower end of the plunger. When the lifter Y is out of the engine a spring wire retainer 12 holds all the parts in the body in an assembled condition. The ball retainer 11 holds a check ball 13 in position over the lower end of a feed hole 14 in the plunger B and limits its travel.

When the valve lifter Y is installed in the engine, the push rod R holds the seat C and plunger B downward clear of the plunger retainer 12 at all times. The plunger spring 10 then presses the lifter body A down against the camshaft X and presses the plunger B and seat C up against the push rod R with a load which is enough to take up all lash clearances between the parts in the valve linkage without affecting positive seating of the valve Z.

Oil is fed to the lifter Y through a gallery 15 in the engine block 16. Oil enters the lifter Y through grooves 17 and 18 in the body A and plunger B respectively, and through oil holes 19 and 20 in the body A and plunger B respectively, and flows down through the plunger B below the seat C and through the feed hole 14 in the plunger. The first few cycles of operation after the engine is started forces out all air and completely fills the plunger Y and the chamber below the plunger B with oil.

At the start of a cycle of valve operation the lifter body rests on the camshaft base circle, as shown. The plunger spring 10 holds all lash clearances out of the valve linkage, and the cheek ball 13 rests on its retainer 11 so that the plunger feed hole 14 is open to permit passage of oil between the plunger B and the chamber below the plunger.

As the rotating camshaft X starts raising the valve lifter body A, oil in the said lower chamber begins to flow through the open feed hole 14, but the flow immediately seats the check ball 13 against the plunger B to prevent appreciable loss of oil from the said lower chamber. The lifting force against the body is then transmitted through the entrapped oil to the check ball 13 and plunger B so that the plunger and push rod seat C move upward with the body to operate the linkage which opens the engine valve Z.

As the camshaft X rotates further to close the engine valve Z, the valve spring (not shown) forces the linkage and lifter Yto follow the cam X downward. When the engine valve Z seats, the linkage parts and lifter plunger B stop, but the plunger spring 10 forces the body A to follow the cam X downward until it again rests on the camshaft base circle (see Fig. 1). Oil pressure against the check ball 13 ceases when the plunger B stops and the check ball 13 drops down against its retainer 11 and the plunger feed hole 14 is again opened to permit passage of oil between the plunger B and the chamber below the plunger.

During the valve opening and closing operation above described, a very slight amount of oil escapes through the clearance between the plunger B and body A an 4 v returns to the crankcase of the engine. This slight loss of oil called leakdown is beneficial and is necessary in providing a gradual change of oil in the lifter Y as fresh oil enters the said lower chamber when the feed hole 14 is opened at the end of each cycle of operation. Opening of the plunger feed hole 14 at the end of each cycle also permits control of the volume of oil in the said lower chamber to compensate for expansion and contraction of the valve linkage parts due to changes in engine temperature.

As shown in Fig. 1 of the drawings, the valve Z is a conventional valve shiftably carried in the head 21 of the engine by a guide 22. A lever assembly is provided in order to transfer the lifting action of the push-rod R to the valve Z and involves a rocker arm-23 pivotally supported by a bearing 24. When the camshaft X operates to lift the lifter Y and push rod R, the rocker arm 23 is rotated and depresses the valve stem to lift the valve Z from the seat 25.

In accordance with the invention the cam follower body A, plunger B and push rod seat C are fabricated of light weight material, for example aluminum or magnesium, in such manner that the density of the material is increased resulting in durable and practical parts. Also, the push rod seat C is fabricated of similar light weight material. It is a feature of construction to also employ wear taking paits of a more dense more durable material in the fabrication of the body A and plunger B with the result that each of these major components is an assembly of parts. That is, the body A and plunger B are each composed of a plurality of parts or elements, the materials forming said parts being selected and employed for lightness and for durability respectively.

The cam follower body A is a cylindrically shaped part that is tubular in cross section and which is closed at its bottom end. In accordance with the invention, the body A is a fabricated structure having a shell-like case 30 and a base 35 at the bottom of the case. The case 30 has an outer cylindrical wall 31 slidably carried in a bore 26 in the engine block 16 and is adapted to reciprocate therein in the usual manner. The base 35 is secured to thelower end of the case 30, as later described, and has a flat cam following face 36 in a plane normal to the axis of the case 30.

The cam follower case 30 is a light weight part and is formed of aluminum. The finished case 30 has a cylindrical bore 32 entering it from the upper end and terminating at a bottom 33. The bottom of the case 30 is engaged with the base 35 while the top terminates at an end 34 there being a suitable snap-ring groove in the bore 32 at the upper end portion thereof to receive the retainer 12. As shown, inner and outer grooves 17 are formed in the inner and outer walls 32 and 31 respectively, and an oil hole 19 extends from the exterior to the interior of the case 30 at the grooves. Said grooves 17 are located substantially midway between the ends of the body A.

The base 35 is a heavy durable part formed in each particular case to be of a material compatible with the material used in the construction of the camshaft X. For example, the base 35 is formed of a cast alloy of iron and is machined to the configuration as shown in Fig. 5. In carrying out the invention, the base 35 is formed with anchoring means 40 therein, said anchoring means being formed in the upper face 37 thereof. The face 37 is preferably a flat face parallel with the face 36, the face 37 being left normally rough, while the face 36 is ground to a smooth finish to engage with the camshaft X. The exterior wall 38 is turned to a diameter coincidental with the outer diameter of the finished lifter Y, and coincidental with the outer wall 31 of the case 30.

The anchoring means 40 may be varied in form and in the preferred form of the invention involves a circular opening 41 that enters the base 35 at the upper face 37. The opening 41 is a channel-shaped opening formed concentrically of the base and has a flat bottom 42 in a plane spaced from and parallel to the face 37. The outer side wall 43 of the opening 41 pitches upwardly and inwardly from the bottom 42 to join the face 37, while the inner side wall 44 of the opening 41 pitches upwardly and outwardly from the bottom 42 to join the face 37. In actual practice the walls are pitched at about 30 so that the opening at the plane of the face 37 is materially restricted.

As best illustrated in Fig. 6 of the drawings, the case 30 is permanently anchored in the base 35 by the means 40 above described. As shown, the case 30 is applied to the base 35 so that the bottom 33 engages the face 37 and so that a portion thereof enters into and occupies the opening 41. By application of downward force at the bottom 33 of the bore in the case 30, the material forming the case is caused to enter into the opening 41 to be accommodated therein and to cooperate with the pitched walls 43 and 44 to permanently couple the case 30 and base 35.

In accordance with the method of the present inven tion, the case 30 of light weight aluminum is worked in the process of assembly with the base 35 so that its density and strength are increased. In carrying out the method, extruding is employed whereby the material is caused to flow into the desired shape by the application of pressure. Suitable die elements (not shown) are employed and the process of impact extrusion is used to cause the flow of material. For instance, a female die is used to receive and support the base 35, said female die having a sized aperture therein to establish the outer cylindrical wall 31 of the case 30. A male die is used to enter the female die and is shaped to establish the inner bore 32 of the case 30. 1

In Fig. 5 of the drawings, I have illustrated a slug S of material, for example 6061 aluminum in the E condition, as it is formed prior to entry into the dies to be extruded thereby, the slug S being related to the base 35 as indicated by the bracket in said figure. The said aluminum alloy that I prefer to use is a hot worked magnesium-silicon base alloy and for instance contains .8 to 1.2% magnesium, .4 to .8% silicon, and .15 to .4% copper, and in addition thereto the aluminum and some impurities. By hot worked I mean that said material is formed into usable shape (as a slug) at 600 F. or above, for instance at 700 F. Note, that the slug S is a straight cylindrically shaped part with flat ends.

As illustrated in Fig. 6, the extruding process forces the material of the slug S to enter the opening 41 in the base 35 and to form the side walls of the case 30. In practice, the male die, or punch, is made with a head of reduced diameter that projects to rough form a spring seat In accordance with the present invention, the slug S is cold worked by the process of impact extrusion and is simultaneously assembled with the base 35. By cold worked I mean that said material is formed into shape at room temperature, or up to temperatures of approximately 300 F.

In order to provide an end product part in the form of a usable and commercially practical case 30, I have found that it is necessary to reduce the material, alumimum, to a substantial degree, and I have found that by cold working said slug S of 6061 aluminum through a range of reduction in area of between 60% to 93% a satisfactory and durable part results. In carrying out the invention, the ideal reduction of material actually employed is 90%, in which case the cross sectional area of the wall of the case 30 is 10% of the cross sectional area of the slug S from which the case 30 is impact extruded (compare Figs. 5 and 6). After the impacting of the slug S into the configuration shown in Fig. 6, the fabrication assembly of the case 30 and base 35 is finished as by machining to the configuration shown in Figs. 2 and 4, and the resulting case 30 is a strong durable part ready for use without the. necessity of heat treatment,

which would not be practical due to the assembly of the iron base 35 with the aluminum case 30.

The plunger B is a cylindrically shaped part that is tubular in cross section and which is closed at its bottom end. In accordance with the invention the plunger B is a fabricated structure having a shell-like sleeve 50 and valve seat 55 at the bottom of the sleeve. The sleeve 50 has an outer cylindrical wall 51 slidably carried in the bore 32 in the body A and is adapted to reciprocate therein in the usual manner. The seat 55 is secured to the lower end of the sleeve 50, as later described, and has a face 56 shaped to have sealing engagement with the check ball 13.

The plunger sleeve 50 is a light weight part and is formed of aluminum. The finished sleeve 50 has a cylindrical bore 52 entering it from the upper end and terminating at a bottom 53. The bottom of the sleeve 50 is engaged with the valve seat 55 while the top terminates at an end 54 adapted to have supporting engagement with the push rod seat C. As shown, a groove i8 is formed in the outer wall 51 and an oil hole 20 extends from the exterior to the interior of the sleeve at the groove. The groove 18 is positioned to register with the grooves 17 in the case 30, as shown.

The valve seat 55 is a heavy durable part formed of a material adapted to withstand continued engagement and disengagement of the check ball 13. For example, the seat 55 is formed of carbon steel bar stock machined to the configuration as shown in Fig. 7. In carrying out the invention, the seat 55 is formed with anchoring means 60 therein, said means being formed in the upper end portion thereof. The valve seat 55 is preferably a round part with a flat top 58. A passage 59 extends through the seat 55 and opens at the face 56, said passage communicating with the interior of the plunger B via the feed hole 14 extending through the bottom 53 of the sleeve 50.

The anchoring means 60 may be varied in form and in the preferred form of the invention involves a head 61 that enters an opening 62 in the bot-tom 53 of the sleeve 50. The head 61 is a tapered head and is cone shaped with an outer wall 63 tapered upwardly and outwardly. serrations 64, or the like, are formed in the upper periphery of the head 61 to prevent rotation between the sleeve 50 and seat 55, and an annular channel is formed in the wall 63 to prevent axial movement of the sleeve 50 and seat 55. In practice, I pitch the wall 63 at about 15 so that the opening 62 is restricted at the lower face of the bottom 53 when the parts are assembled as later described.

As best illustrated in Fig. 3 of the drawings, the sleeve 50 is permanently anchored to the seat 55 by the means 60 above described. As shown, the sleeve 50 is applied to the seat 55 so that the head 61 occupies the opening 62 and so that the material forming the sleeve 50 enters between the serrations 64 and enters the channel 65. By application of inward force at the bottom 53 of the sleeve 50, the material forming the sleeve is caused to enter between the serrations 64 and into the channel 65 to cooperate with the head 61 in a manner to permanently couple the sleeve 50 and seat 55.

- In accordance with the method of the present invention, the sleeve 50 of light weight aluminum is worked in the process of assembly with the seat 55 so that its density and strength is increased. In carrying out the method, extruding is employed whereby the material is caused to flow into the desired shape by the application of pressure. Suitable die elements (not shown) are employed and the process of impact extrusion is used to cause the flow of material. For instance, a female die is used to receive and support the seat 55, said female die having a sized aperture that establishes the outer cylindrical wall 51 of the sleeve 50. A male die is used to enter the female die and is shaped to establish the inner bore52 of the sleeve 50.

a 7 In Fig.- 7 of the drawings I have illustrated a slug 8' of material, for example 6061 aluminum in the F condition as it is formed prior to entry into the dies to be extruded thereby, the slug S being related to the seat 55 as indicated by the bracket in said figure. The said aluminum alloy that I prefer to use in the slug S is a hot worked magnesium-silicon base alloy the same as above set forth in connection with the case 30. Note that the slug S is a straight cylindrical slug with flat ends.

As illustrated, in Fig. 3, the extruding process forces the material of the slug S to enter the elements of the anchor 60 and to form the side wall of the sleeve 50. In accordance with the present invention, the slug S is cold Worked by the process of impact extrusion and is simultaneously assembled with the seat 55. By cold worked I mean that said material is formed into shape at room temperature or up to temperatures of approximately 300 F. the same as above described in connection with the case 30.

In order to provide an end product part in the form of a usable and commercially practical sleeve 50 I have found that it is necessary to reduce the material, aluminum, the same as above described in connection with the case 30. That is, the aluminum is cold worked" between 60% to 93%, and perferably, and for instance, 90%, whereby the cross sectional area of the wall of the sleeve 50 is of the cross sectional area of the slug S from which the sleeve 50 is impact extruded (compare Figs. 7 and 9). After the impacting of the slug S into the configuration shown in Fig. 9 the fabricated assembly of the sleeve 50 and seat 55 is finished as by machining to the configuration shown in Figs. 2 and 3, and the resulting sleeve 50 is a strong durable part ready for use without the necessity of heat treating, which Would not be practical for the same reason as above pointed out in connection with the case 30.

The push-rod seat C is shaped to the usual configuration with a downwardly faced shoulder 70 having supporting engagement with the top end 54 of the plunger B and with a spherical upwardly faced seat 72 adapted to have end engagement with the push rod R. In practice, the seat C is formed of 6061 aluminum by an-impact process, as above described in connection with the body A and plunger B, in order to compact the material and to the end that it is more dense and of suitable hardness and durability.

The components A, B and C are made to the desired tolerances and the body A and plunger B are selectively matched so that the desired leakdown is attained. The said lightweight components formed of material such as aluminum or magnesium are treated to have a protective coating 100, and in the case under consideration the aluminum parts are hard anodized to have a surface hardness in excess of 70 on the Rockwell C scale. For example, the matching body wall 32 and plunger wall 51 are centerless ground and are then anodized increasing the wall thickness as much as from .0004 to .0008 ofan inch, after which the wall thickness (the anodizing) is reduced a few ten thousandths of an inch by finish lapping.

With the body A and plunger B fabricated and strengthened as hereinabove described, an extremely durable and practical hydraulic valve lifter unit Y is obtained. By increasing the density and hardness of the otherwise relatively soft aluminum, through work hardening during the process of impact extrusion and by anodizing, sufliciently high physical properties are realized in the aluminum in order to serve reliably under all operating conditions. By assembling the parts by employing the flow of material into the undercut anchoring means above described, permanent joinder of the parts is realized without danger of separation thereof. Further, the softness of the aluminum is not detrimental since by surfacing the parts as by hard anodizing the body A and plunger B are made very durable, and accuracy of fit, "or match- 8 ing, is attained by lapping the critical working surfaces after said anodizing.

The light weight valve lifter unit Y that I provide is extremely useful and its use improves the action of the valve train in which it is used. The low inertia value in the unit per se also makes possible the manufacture of other valve train parts of low inertia value, to the end that the overall operation of the valve train, and operation of the internal combustion engine as a whole, is more eflicient. In carrying out the invention, each unit of said lifter Y of conventional automotive size weighs approximately 1152 grains.

Having described only a typical preferred form and application of my invention, I do not wish to be limited 'or restricted to the specific details herein set forth, but

wish to reserve to myself any variations or modifications that may appear to those skilled in the art and fall within the scope of the-following claims.

Having described my invention, I claim:

1. A hydraulic valve lifter unit having a cam follower, a low inertia plunger operating in the follower, a pushrod seat engaged with the plunger, and means controlling flow of fluid at the plunger to cause movement of the push-rod seat when the follower is shifted, said plunger including, a valve seat formed of material adapted to "cooperatively engage with a check ball and having an anchor head formed thereon, and a tubular sleeve of light Weight material projecting from and having a bottom with an opening therein engaged with said head, said head 'having peripheral serrations preventing rotation between the sleeve and the seat.

2. A hydraulic valve lifter unit having a cam follower, a low inertia plunger operating in the follower, a push-rod seat engagedwith the plunger, and means controlling flow of fluid at the plunger to cause movement of the push-rod seat when the follower is shifted, said plunger including, a valve seat formed of material adapted to cooperatively engage with a check ball and having an anchor head formed thereon, and a tubular sleeve of light weight material projecting from and having a bottom with an opening therein engaged with said head, said head having an outwardly disposed channel formed in the periphery thereof preventing axial displacement of the sleeve and the seat.

3. A hydraulic valve lifter unit having a low inertia cam follower, a low inertia plunger operating in the follower, a push-rod seat engaged with the plunger, and means controlling flow of fluid at the plunger to cause movement of the push-rod seat when the follower is shifted, said follower including, a base formed of material to be compatible with a cam, and a case projecting from the base and formed of anodized aluminum, said plunger including, a valve seat formed of material adapted to cooperatively engage with a check ball, and a sleeve projecting from the seat and formed of anodized aluminum.

4. A hydraulic valve lifter unit having a low inertia cam follower, a low inertia plunger operating in the follower, a push-rod seat engaged with the plunger, and means controlling flow of fluid at the plunger to cause movement of the push-rod seat when the follower is shifted, said follower including, a disc-shaped base formed of material to be compatible with a cam and having an opening with inclined walls formed therein, and a tubular case of light weight material projecting from and having a bottom with a portion thereof engaged with the walls in said opening and joining the case to the base, said plunger including, a valve seat formed of material adapted to cooperatively engage with a check ball and having an anchor head formed thereon, and a tubular sleeve of light weight material projecting from and having a bottom with an opening therein engaged with said head, said head having peripheral serrations preventing rotation between the sleeve and the seat.

5. The method:of fabricating a' cam follower of th character described and having a disc-shaped base of relatively hard material compatible with a cam and a case of relatively soft light weight aluminum alloy projecting from the base, and including, forming an opening in the base, and then forming a slug of said aluminum into the configuration of the case by the application of pressure and substantial reduction in area, whereby a portion of said slug material enters into the opening in the base to permanently couple the base to the case and whereby thedensity and strength of said aluminum is substantially increased.

6. The method of fabricating a cam follower of the character described and having a disc-shaped base of relatively hard material compatible with a cam and a case of relatively soft light weight aluminum alloy projecting from the base, and including, forming an opening with undercut walls in the base, and then forming a slug of said aluminum into the configuration of the case by the application of pressure and at least 60% reduction in area, whereby a portion of said slug material enters into the opening to engage said walls in the base to permanently couple the base to the case and whereby the density and strength of said aluminum is substantially increased.

7. The method of fabricating a cam follower of the character described and having a disc-shaped base of relatively hard material compatible with a cam and a case of relatively soft light weight aluminum alloy projecting from the base, and including, forming an opening in the base and supporting the base in a die part, and then forming a slug of said aluminum alloy into the configuration of the case by application of pressure through movement of a second die part relative to the first mentioned die part and through a reduction in area of at least 60%, whereby a portion of said slug material enters into the opening in the base to permanently couplc the base to the case and whereby the density and strength of said aluminum is substantially increased.

8. The method of fabricating a plunger of the character described and having a valve seat of relatively hard material adapted to cooperatively engage with a check ball and with a head and having a sleeve of relatively soft light weight aluminum alloy projecting from the seat, and including, forming a slug of said aluminum into the configuration of the sleeve by the application of pressure and substantial reduction in area, whereby a portion of said slug material encompasses the head of the valve seat to permanently couple the seat to the sleeve and whereby the density and strength of said aluminum is substantially increased.

9. The method of fabricating a plunger of the character described and having a valve seat of relatively hard material adapted to cooperatively engage with a check ball and with a head and having a sleeve of relatively soft light weight aluminum alloy projecting from the seat, and including, supporting the valve seat in a die part, and forming a slug of said aluminum into the configuration of the sleeve by the application of pressure through movement of a second die part relative to the first mentioned die part and through a reduction in area of at least whereby a portion of said slug material encompasses the head of the valve seat to permanently couple the seat to the sleeve and whereby the density and strength of said aluminum is substantially increased.

References Cited in the file of this patent UNITED STATES PATENTS 1,848,083 Wetherald Mar. 1, 1932 1,916,191 Burkhardt July 4, 1933 2,790,430 Lowther Apr. 30, 1957 2,797,673 Black July 2, 1957 2,812,750 Lesher Nov. 12, 1957 FOREIGN PATENTS 1,020,632 France Nov. 19, 1952 

